VAX-11/RSX-11M

This "VAX-11/RSX-11M Programmer's Reference Manual" from August 1978 serves as a compatibility guide for RSX-11M programmers seeking to run their Version 3.1 task images under the VAX/VMS operating system on a VAX-11/780 processor.

The document explains how VAX/VMS achieves this compatibility by emulating the RSX-11M executive directives and environment, primarily through hardware-generated traps that allow VAX/VMS to perform the requested service in its native mode. It details the mapping of RSX-11M concepts (like tasks) to VAX/VMS equivalents (processes and images), and how RSX-11M's I/O operations are translated and handled by the VAX/VMS I/O system, including device assignment, queue I/O requests, and interprocess communication via mailboxes.

Crucially, the manual highlights key differences and limitations: VAX/VMS does not fully duplicate the entire RSX-11M operating system environment. Features like partitions, significant events, specific memory management directives (PLAS), and certain priority handling are either not emulated, result in no operation (while returning a success status to allow execution to continue), or return specific error codes. It provides detailed descriptions of supported and unsupported RSX-11M directives, including their VAX/VMS equivalents and any behavioral changes or prerequisites (e.g., task names for common event flags or mailbox-based communication). The goal is to provide RSX-11M programmers with the necessary information to adapt their programs for successful execution on the VAX/VMS platform.